refactor(arap): rustfmt the unit's files, and the write-off's SOURCE line (P4b S7)

No behaviour: the files as rustfmt leaves them after the unit's edits
(the commits before this one were made before the formatter ran), and the
Ledger::write_off spec block cites A-5 alone for the direct write-off
method (A-6 is the hand-entry refusal, not this command).

crates/ledger-store/src/lib.rs

@@ -49,6 +49,6 @@ pub use snapshot::{DiskCheck, Snapshot};
 pub use store::{
     Attachment, BillPreview, DepreciationRun, DisposalPreview, EntryRow, EventRow, InvoicePreview,
     JOURNAL_FILE, LEGACY_DB_FILE, LOCK_FILE, MAX_RECURRING_RUN, PayrollLineInput, Reconciliation,
-    Statement, Store, Subject, VerifyReport, WriteOffEvidence, database_in_use, db_file, db_file_for,
-    is_database_file,
+    Statement, Store, Subject, VerifyReport, WriteOffEvidence, database_in_use, db_file,
+    db_file_for, is_database_file,
 };

crates/ledger-store/src/store.rs

@@ -3747,13 +3747,8 @@ impl Store {
         let description = format!("Write off invoice {invoice}: {}", reason.trim());
         let (entry_id, mut journaled) =
             self.journal_auto_entry(date, &description, bad, ar, amount)?;
-        let written_off = crate::meta::invoice_written_off(
-            invoice,
-            entry_id,
-            date,
-            amount,
-            reason.trim(),
-        );
+        let written_off =
+            crate::meta::invoice_written_off(invoice, entry_id, date, amount, reason.trim());
         journaled.push(self.append_journal("invoice.written_off", written_off)?);
         let live = self.ledger.write_off(invoice, date, amount, reason)?;
         debug_assert_eq!(live, entry_id, "id allocator diverged from journal");